Micromachined multi-axis gyroscopes with reduced stress sensitivity

ABSTRACT

In a general aspect, a micromachined gyroscope can include a substrate and a static mass suspended in an x-y plane over the substrate by a plurality of anchors attached to the substrate. The static mass can be attached to the anchors by anchor suspension flexures. The micromachined gyroscope can include a dynamic mass surrounding the static mass and suspended from the static mass by one or more gyroscope suspension flexures.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/143,772, filed on Sep. 27, 2018 (now U.S. Pat. No. 11,085,766), whichclaims priority to and the benefit of U.S. Provisional Application No.62/584,361, filed on Nov. 10, 2017, and entitled “MICROMACHINEDMULTI-AXIS GYROSCOPES WITH REDUCED STRESS SENSITIVITY,” both of whichare incorporated by reference herein in their entireties.

TECHNICAL FIELD

The present disclosure relates to micro machined multi-axis gyroscopes.

BACKGROUND

A micromachined gyroscope is a type of inertial sensor which can be usedto measure angular rate or attitude angle. Several single-axis ormulti-axis micromachined microelectromechanical systems (MEMS)gyroscopes have been integrated into various systems (e.g., systems forbalance, guidance or navigation). As the size of such gyroscopes becomessmaller and the desired sensitivity increases, small scale stresses oncertain components of the gyroscopes can detract from the accuracy ofthe sensors.

SUMMARY

In a general aspect, a micromachined gyroscope can include a substrateand a static mass suspended in an x-y plane over the substrate by aplurality of anchors attached to the substrate. The static mass can beattached to the anchors by anchor suspension flexures. The micromachinedgyroscope can include a dynamic mass surrounding the static mass andsuspended from the static mass by one or more gyroscope suspensionflexures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustration of a 3-degrees-of-freedom (3-DOF) inertialmeasurement unit (IMU), in accordance with the principles of the presentdisclosure.

FIG. 2A is an illustration of an example Inner Electrode versiongyroscope, in accordance with the principles of the present disclosure.

FIG. 2B is an illustration of comb finger structures of a clockwisedrive and an anticlockwise drive actuator, a drive oscillation senseelectrode, and a Z-axis rate sense electrode, in accordance with theprinciples of the present disclosure.

FIG. 3A is an illustration of views of clockwise and counterclockwiserotations of the example Inner Electrode version gyroscope (of FIG. 2A)by the clockwise drive actuator and the anticlockwise drive actuator, inaccordance with the principles of the present disclosure. FIG. 3B is anillustration of central suspension flexures at the center of a gyroscope(of FIG. 2A) under the rotation, in accordance with the principles ofthe present disclosure.

FIG. 3C is an illustration of Z-axis rate sensing in the gyroscope ofFIG. 2A, in accordance with the principles of the present disclosure.

FIG. 4 is an illustration of X-axis and Y-axis rate sensing in thegyroscope, in accordance with the principles of the present disclosure.

FIG. 5A is a schematic view of a finite element simulation of a testscenario in which stress on a gyroscope substrate (in the gyroscope ofFIG. 2A) is modelled as an out-of-plane deformation of a single anchor,in accordance with the principles of the present disclosure.

FIG. 5B is cross sectional view of the finite element simulation of thetest scenario (of FIG. 5A) in which stress on a gyroscope substrate ismodelled as an out-of-plane deformation of a single anchor, inaccordance with the principles of the present disclosure.

FIG. 6 is an illustration of an example Outer Electrode versiongyroscope, in accordance with the principles of the present disclosure.

FIG. 7A is an illustration of views of clockwise and counterclockwiserotations of the example Outer Electrode version gyroscope (of FIG. 6)by the clockwise drive actuator and the anticlockwise drive actuator, inaccordance with the principles of the present disclosure.

FIG. 7B is an illustration of the gyroscope central suspension flexuresat the center of the gyroscope under rotation (of FIG. 7A), inaccordance with the principles of the present disclosure.

FIG. 7C is an illustration of Z-axis rate sensing in the gyroscope ofFIG. 6, in accordance with the principles of the present disclosure.

FIG. 8 is an illustration of X-axis and Y-axis rate sensing in thegyroscope of FIG. 6, in accordance with the principles of the presentdisclosure.

FIG. 9 is a schematic view of a finite element simulation of a testscenario in which stress on a gyroscope substrate (in the gyroscope ofFIG. 6) is modelled as an out-of-plane deformation of a single anchor,in accordance with the principles of the present disclosure.

FIG. 10 illustrates an example method for mitigating or averagingdeformation displacements across a substrate in a micromachinedgyroscope.

DETAILED DESCRIPTION

Micromachined gyroscopes include mechanical components that can be madeof silicon. These mechanical structures may include components that havedimensions on the order of a few to tens of microns thick. Commonly,micromachined gyroscopes are enclosed in MEMS packages, which arefabricated using, for example, off-the-shelf packaging techniques andmaterial derived from the semiconductor microelectronics field. A MEMSpackage may provide, for example, some mechanical support, protectionfrom the environment, and electrical connection to other systemcomponents. However, in the field, the MEMS package may itself besubject to mechanical and or thermal stress, which can propagate to andwarp the enclosed gyroscope substrate and components. Such packaginginduced stress or substrate stress induced deformation of gyroscopecomponents remains a concern (e.g., for high performance gyroscopes)since it directly affects the performance of the enclosed micromachinedgyroscope in operation.

This disclosure describes example micromachined multi-axis gyroscopestructures formed in an x-y plane of a device layer that have reducedsensitivity to substrate stress or deformation.

In an example, a 3-axis gyroscope may have a single planar proof massdesign providing 3-axis gyroscope operational modes. The planarproof-mass in the device layer can be symmetrically suspended from asubstrate (or anchored to substrate) using a configuration ofgeometrically-distributed anchors and one or more symmetrical flexurebearings (which can be referred to as flexures), in accordance with theprinciples of the present disclosure. In an example implementation theplanar proof-mass is suspended from a set of four anchors attached tothe substrate. Further, the flexures can include x, y, and z-axisflexure bearings.

The multiple geometrically-distributed anchors can track substratedeformation and can physically modify the out-of-plane capacitive gapsof measurement electrodes in the gyroscope that measure X-axis andY-axis rates (accelerations) of the proof mass to compensate for thesubstrate deformation. For example, the out-of-plane capacitive gaps ofthe electrodes can be averaged across two anchors in each of the X and Ydimensions.

FIG. 1 is a schematic cross-sectional view of a 3-degrees-of-freedom(3-DOF) inertial measurement unit (IMU) 100, in accordance with theprinciples of the present disclosure.

IMU 100 includes a 3-DOF gyroscope or a 3-DOF micromachinedaccelerometer, formed in a chip-scale package including a cap wafer 101,a device layer 105 including micromachined structures (e.g., amicromachined 3-DOF IMU), and a substrate or via wafer 103. Device layer105 can be sandwiched between cap wafer 101 and via wafer 103, and thecavity between device layer 105 and cap wafer 101 can be sealed undervacuum at the wafer level.

In an example, cap wafer 101 can be bonded to the device layer 105using, for example, a metal bond 102. Metal bond 102 can include afusion bond, such as a non-high temperature fusion bond, to allow getterto maintain long term vacuum and application of anti-stiction coating toprevent stiction that can occur to low-g acceleration sensors. In anexample, during operation of device layer 105, metal bond 102 cangenerate thermal stress between cap wafer 101 and device layer 105. Incertain examples, one or more features can be added to device layer 105to isolate the micromachined structures in the device layer 105 fromthermal stress, such as one or more stress reducing grooves formedaround the perimeter of the micromachined structures. In an example, viawafer 103 can be bonded to device layer 105 (e.g., silicon-siliconfusion bonded, etc.) to obviate thermal stress between via wafer 103 anddevice layer 105.

In an example, via wafer 103 can include one or more isolated regions,such as a first isolated region 107, isolated from one or more otherregions of via wafer 103, for example, using one or morethrough-silicon-vias (TSVs), such as a first TSV 108 insulated from viawafer 103 using a dielectric material 109. In certain examples, the oneor more isolated regions can be utilized as electrodes to sense oractuate out-of-plane operation modes of the 3-axis inertial sensor, andthe one or more TSVs can be configured to provide electrical connectionsfrom device layer 105 outside of IMU 100. Further, via wafer 103 caninclude one or more contacts, such as a first contact 110, selectivelyisolated from one or more portions of via wafer 103 using a dielectriclayer 104 and configured to provide an electrical connection between oneor more of the isolated regions or TSVs of via wafer 103 to one or moreexternal components, such as an ASIC wafer, using bumps, wire bonds, orone or more other electrical connection.

In accordance with the principles of the present disclosure, a3-degrees-of-freedom (3-DOF) gyroscope or the micromachinedaccelerometer in device layer 105 can be supported or anchored to viawafer 103 by bonding device layer 105 to a plurality of protrudingportions of via wafer 103 (e.g., anchor 106 a and anchor 106 b that areseen in the cross sectional view of FIG. 1). The plurality of protrudingportions of via wafer 103 (e.g., anchor 106 a and anchor 106 b) arelocated at a substantial distance from the center of the via wafer 103,and device layer 105 can, for example, be fusion bonded to the anchor106 a and anchor 106 b (e.g., to eliminate problems associated withmetal fatigue).

In an example implementation, four off-center anchors can besymmetrically located at corners of a geometrical square (i.e., witheach anchor being at a same radial distance from the center of thesquare) to support the gyroscope or the micromachined accelerometer indevice layer 105 on the substrate (i.e., wafer 103). The four off-centeranchors may include the two anchors (i.e., anchor 106 a and anchor 106b) seen in the cross sectional view of FIG. 1, and two anchors (notshown) that are in a plane perpendicular to FIG. 1.

The 3-degrees-of-freedom (3-DOF) gyroscope structures described hereinhave two masses in the X-Y plane: a dynamic or proof mass, which isdriven to resonance (e.g., by drive electrodes), and a static mass toserve as a platform. The dynamic mass is connected to the static mass,and the static mass is connected to the substrate. The platform isanchored to the substrate at four locations of the symmetrically placedfour off-center anchors. The suspension of the platform and connecteddynamic mass from the geometrically distributed four anchors effectivelyaverages the out-of-plane displacement of the dynamic mass with respectto stress-induced substrate warpage or bending of the substrate acrossthese four locations, thus reducing asymmetric gap changes due tostress.

The 3-degrees-of-freedom (3-DOF) gyroscope in device layer 105 may beimplemented as an Inner Electrode version or as an Outer Electrodeversion of the gyroscope in device layer 105. While the mechanism ofstress sensitivity reduction is similar in both versions, a primarydifference between the two versions is the placement of the out-of-planeelectrodes in the gyroscope. Inner Electrode version: The pairs ofout-of-plane X axis electrodes and Y axis electrodes (on wafer 103) areplaced close to the center of the gyroscope. Outer Electrode version:The pairs of out-of-plane X axis electrodes and Y axis electrodes (onwafer 103) are placed away from the center and toward the edges of thegyroscope.

An example Inner Electrode version gyroscope 200 is shown in FIG. 2A, inaccordance with the principles of the present disclosure.

Inner Electrode version gyroscope 200, which may be fabricated in adevice layer (e.g., device layer 105, FIG. 1), includes a static mass201 and a dynamic mass 202 in the X-Y plane. Static mass 201, which mayhave an X shape o (a cross shape) is supported on the substrate (e.g.,wafer 13) by four off-center anchors (e.g., anchors 21 a, 21 b, 21 c,and 21 d) via anchor suspension flexures (e.g., flexure 22). In exampleimplementations, flexure 22 may include one more rectangular elastichinges 22 e (e.g., as shown in FIG. 2B). Dynamic mass 202 is suspendedaround static mass 201 via gyroscope central suspension flexures 23.Gyroscope central suspension flexures 23 which may be C-beam flexures,attach dynamic mass 202 to static mass 201 at about the bottoms of thefour valleys of the X-shape of static mass 201. In exampleimplementations, gyroscope central suspension flexures 23 may includeone or more C-shape elements (i.e., C-beam flexures 23 c) (FIG. 3B).

In the example inner electrode version gyroscope 200, out-of-planeX-axis sense electrodes 27 and Y-Axis sense electrodes 28 (which aredisposed on wafer 103 below device layer 105) are placed close to thecenter of gyroscope 200 (e.g., at about midway between a center 35 andan edge 37 of gyroscope 200). Further, the center-of-mass of the X-Axisand Y-Axis sense electrodes are placed at the same radial distance fromthe center of gyroscope 200 as the four anchors (i.e. anchors 21 a, 21b, 21 c, and 21 d).

Gyroscope 200 also includes various in-plane drive and sensingelectrodes. For example, gyroscope 200 includes two pairs of driveelectrodes (e.g., a pair of clockwise drive actuators 24 and a pair ofanti-clockwise drive actuators 25), a pair of sensing electrodes (e.g.,drive oscillation sense electrodes 26), and a pair of Z-axis rate senseelectrodes 29 that are disposed at distances from the center ofgyroscope 200 toward the outer edges (e.g., edge 37) of gyroscope 200.Clockwise drive actuators 24, anti-clockwise drive actuators 25, driveoscillation sense electrodes 26, and Z-axis rate sense electrodes 29can, for example, be comb finger structures. FIG. 2B, for purposes ofillustration of these comb finger structures, shows exploded views of aclockwise drive actuator 24, a drive oscillation sense electrode 26, anda Z-axis rate sense electrode 29.

In gyroscope 200, the various in-plane drive and sensing electrodes(e.g., clockwise drive actuators 24, anti-clockwise drive actuators 25,drive oscillation sense electrodes 26, and Z-axis rate sense electrodes29) are attached to the substrate (e.g., wafer 103), for example, viaanchors (e.g., anchors 30).

A Z-axis rotary oscillation mode of gyroscope 200 can be actuated, forexample, by using clockwise drive actuator 24 to drive dynamic mass 202(which is suspended symmetrically about the four anchors 21 a-21 d) in aclockwise direction, and using anti-clockwise drive actuator 25 to drivedynamic mass 202 in an anti-clockwise direction. Drive oscillation senseelectrodes 26 can sense oscillation of dynamic mass 202 and providefeedback to a drive circuit (not shown) that drives clockwise driveactuators 24 and anti-clockwise drive actuator 25 to, for example, drivedynamic mass 202 to resonance.

FIG. 3A shows views of clockwise and counterclockwise rotations of theexample Inner Electrode version gyroscope (of FIG. 2A) by the clockwisedrive actuator and the anticlockwise drive actuator, in accordance withthe principles of the present disclosure.

FIG. 3A, in row A, shows views of the gyroscope being rotated clockwiseand counterclockwise by clockwise drive actuators 24 and theanticlockwise drive actuators 25, respectively. Further, FIG. 3A, in rowB, shows views of a modeled simulation of the displacements of thegyroscope being rotated clockwise and counterclockwise by clockwisedrive actuators 24 and the anticlockwise drive actuators 25,respectively. (In FIG. 3A, row B, darker shading indicates lowdisplacement values and lighter shading indicates high displacementvalues)

In operation, a Z-axis rotary oscillation drive on gyroscope 200 can bea high amplitude drive. The symmetric c-beam flexures (gyroscope centralsuspension flexures 23) at the center of gyroscope 200 providemechanical quadrature cancellation (as illustrated in exploded view, forexample, in FIG. 3B).

Further, in-plane differential comb finger electrodes for Z-Axis RateSense (i.e., Z-axis rate sense electrodes 29) can be used to sense aCoriolis rate response.

FIG. 3C, in row A, shows examples of the compressive and expansivemotion of the gyroscope (of FIG. 2A) driven by Z-axis rate senseelectrodes 29 to sense the Coriolis rate response, in accordance withthe principles of the present disclosure. Further, FIG. 3C, in row B,shows views of a modeled simulation of the displacements of thegyroscope driven by Z-axis rate sense electrodes 29 to sense theCoriolis rate response. (In FIG. 3C, row B, darker shading indicateslower displacement values and lighter shading indicates higherdisplacement values).

Further, the out-of-plane X-Axis rate sense electrodes (i.e., electrodes27 (X−) and 27 (X+)) and out-of-plane Y-Axis rate sense electrodes(i.e., electrodes 28 (Y−) and 28 (Y+) can sense the Coriolis rateresponse (as shown, for example, in FIG. 4).

FIG. 4, in row A, shows in perspective view, two examples of the motionof the gyroscope (of FIG. 2A) driven by X-axis rate sense electrodes 27and Y-axis rate sense electrodes 28, respectively, to sense the Coriolisrate response, in accordance with the principles of the presentdisclosure. Further, FIG. 4, in row B, shows, views of a modeledsimulation of the displacements of the gyroscope driven by X-axis ratesense electrodes 27 and Y-axis rate sense electrodes 28, respectively,to sense the Coriolis rate response. Further, FIG. 4, in row C, showscross sectional views of the modeled simulation of the displacements ofthe gyroscope (shown in row B) driven by X-axis rate sense electrodes 27and Y-axis rate sense electrodes 28, respectively, to sense the Coriolisrate response. (In FIG. 4, row B and row C, darker shading indicateslower displacement values and lighter shading indicates higherdisplacement values).

FIG. 5A is schematic view of a finite element simulation of a testscenario in which stress on the substrate (e.g., wafer 13) is modelledas an extreme out-of-plane deformation of a single anchor (e.g., anchor21 a) of the four anchors (e.g., anchors 21 a, 21 b, 21 c, and 21 d) onwhich gyroscope 200 is suspended (FIG. 2A). FIG. 5B is cross sectionalview of the finite element simulation of the test scenario (of FIG. 5A)in which stress on a gyroscope substrate is modelled as an out-of-planedeformation of a single anchor.

As a result of the out-of-plane anchor deformation, nominally planargyroscope components (i.e. static mass 201 and dynamic mass 202) arealso deformed. FIGS. 5A and 5B show, for example, static mass 201 asbeing noticeably deformed. However, because of the geometricallydistributed suspension of the gyroscope components on multiple anchors(e.g., the four anchors 21 a, 21 b, 21 c, and 22 d) there is reducedsensitivity of the out-of-plane rate sense electrodes of both X and Yaxis (i.e., electrodes 27 (X−) and 27 (X+), and electrodes 28 (Y−) and28 (Y+)) to the deformation. The four anchors track substratedeformation and average the capacitive gaps (between the out-of-planerate sense electrodes and dynamic mass 202) to mitigate the differencesin deformation displacements.

An example Outer Electrode version gyroscope 600 is shown in FIG. 6, inaccordance with the principles of the present disclosure. OuterElectrode version gyroscope 600, which may be fabricated in a devicelayer (e.g., device layer 105, FIG. 1), includes a static mass 601 and adynamic mass 602 in the X-Y plane. Static mass 601, which may have an Xor a cross shape is supported on the substrate (e.g., wafer 13) by fouroff-center anchors (e.g., anchors 61 a, 61 b, 61 c, and 61 d) via anchorsuspension flexures (e.g., flexure 62). Dynamic mass 602 is suspendedaround static mass 201 via gyroscope central suspension flexures 63.Gyroscope central suspension flexures 63, which may be C-beam flexures,attach dynamic mass 602 to static mass 601 at about the bottoms of thefour valleys of the X-shape of static mass 601.

In the example Outer Electrode version gyroscope 600, out-of-planeX-Axis rate sense electrodes (i.e., electrodes 67 (X−) and 67(X+)) andout-of-plane Y-Axis rate sense electrodes (i.e., electrodes 68 (Y−) and68 (Y+) (which are disposed on wafer 103 below device layer 105) areplaced close to the outer edges of gyroscope 600 away from the center ofgyroscope 600.

Gyroscope 600 also includes various in-plane drive and sensingelectrodes. For example, gyroscope 600 includes a pair of driveelectrodes (e.g., clockwise drive actuator 64 and an anti-clockwisedrive actuator 65), a pair of sensing electrodes (e.g., driveoscillation sense electrodes 26), and a pair of Z-axis rate senseelectrodes 69 that are disposed toward the outer edges of gyroscope 200away from the center of gyroscope 200. Clockwise drive actuator 64,anti-clockwise drive actuator 65, a pair of drive oscillation senseelectrodes 66, and a pair of Z-axis rate sense electrodes 69 can, forexample, be comb finger structures.

The various in-plane drive and sensing electrodes (e.g., clockwise driveactuator 64, anti-clockwise drive actuator 65, drive oscillation senseelectrodes 66, and Z-axis rate sense electrodes 69) are attached to thesubstrate (e.g., wafer 103), for example, via anchors (e.g., anchors70).

A Z-axis rotary oscillation mode of gyroscope 600 can be actuated, forexample, by using clockwise drive actuator 64 to drive dynamic mass 602(which is suspended symmetrically about the four anchors 61 a-61 d) in aclockwise direction, and using anti-clockwise drive actuator 65 to drivedynamic mass 602 in an anti-clockwise direction. Drive oscillation senseelectrodes 66 can sense drive oscillation and provide feedback to adrive circuit (not shown) that drives clockwise drive actuator 64 andanti-clockwise drive actuator 65.

FIG. 7A shows views of clockwise and counterclockwise rotations of theexample Outer Electrode version gyroscope (of FIG. 6) by the clockwisedrive actuator and the anticlockwise drive actuator, in accordance withthe principles of the present disclosure.

FIG. 7A, in row A, shows views of the gyroscope being rotated clockwiseand counterclockwise by clockwise drive actuator 64 and theanticlockwise drive actuators 65, respectively. Further, FIG. 7A, in rowB, shows, views of a modeled simulation of the displacements of thegyroscope being rotated clockwise and counterclockwise by clockwisedrive actuators 64 and the anticlockwise drive actuators 65,respectively. (In FIG. 7A, row B, darker shading indicates lowdisplacement values and lighter shading indicates high displacementvalues).

In operation, a Z-axis rotary oscillation drive on gyroscope 600 can bea high amplitude drive. The symmetric C-beam flexures (gyroscope centralsuspension flexures 63) at the center of gyroscope 600 providemechanical quadrature cancellation (as illustrated in exploded view, forexample, in FIG. 7B).

Further, in-plane differential comb finger electrodes for Z-Axis ratesense (i.e., Z-axis rate sense electrodes 69) can be used to sense aCoriolis rate response of gyroscope 600.

FIG. 7C, in row A, shows examples of the compressive and expansivemotion of the gyroscope (of FIG. 6) driven by Z-axis rate senseelectrodes 69 to sense the Coriolis rate response, in accordance withthe principles of the present disclosure. Further, FIG. 7C, in row B,shows views of a modeled simulation of the displacements of thegyroscope driven by Z-axis rate sense electrodes 69 to sense theCoriolis rate response. (In FIG. 7C, row B, darker shading indicateslower displacement values and lighter shading indicates higherdisplacement values).

Additionally, the out-of-plane X-Axis rate sense electrodes (i.e.,electrodes 67 (X−) and 67 (X+)) and out-of-plane Y-Axis rate senseelectrodes (i.e., electrodes 68 (Y−) and 68 (Y+) can sense the Coriolisrate response (as shown, for example, in FIG. 8).

FIG. 8, in row A, shows perspective views of two examples of the motionof the gyroscope (of FIG. 6) driven by X-axis rate sense electrodes 67and Y-axis rate sense electrodes 68, respectively, to sense the Coriolisrate response, in accordance with the principles of the presentdisclosure. Further, FIG. 8, in row B, shows views of a modeledsimulation of the displacements of the gyroscope driven by X-axis ratesense electrodes 67 and Y-axis rate sense electrodes 68, respectively,to sense the Coriolis rate response. Further, FIG. 8, in row C, showscross sectional views of the modeled simulation of the displacements ofthe gyroscope (shown in row B) driven by X-axis rate sense electrodes 67and Y-axis rate sense electrodes 68, respectively, to sense the Coriolisrate response. (In FIG. 8, row B and row C, darker shading indicateslower displacement values and lighter shading indicates higherdisplacement values).

FIG. 9 is schematic view of a finite element simulation of a testscenario in which stress on the substrate (e.g., wafer 13) of gyroscope600 is modelled as an extreme out-of-plane deformation of a singleanchor (e.g., anchor 61 a) of the four anchors (e.g., anchors 61 a, 61b, 61 c, and 62 d) on which gyroscope 600 is suspended (FIG. 6). Twoperspective views and a cross sectional view of the simulated gyroscope600 are shown FIG. 9.

As discussed above in the case of gyroscope 200, because of thesuspension of gyroscope 600 on geometrically distributed multipleanchors (e.g., the four anchors 61 a, 61 b, 61 c, and 62 d) there isreduced sensitivity of the out-of-plane rate sense electrodes of both Xand Y axis (i.e., electrodes 67 (X−) and 67 (X+), and electrodes 68 (Y−)and 68 (Y+)) to the deformation. The four anchors track substratedeformation and average the capacitive gaps (between the out-of-planerate sense electrodes and dynamic mass 602) to mitigate the differencesin deformation displacements across the substrate.

FIG. 10 shows an example method 1000 for mitigating or averagingdeformation displacements across a substrate in a micromachinedgyroscope.

Method 1000 includes suspending a static mass of a micromachinedgyroscope in an x-y plane over a substrate by a plurality of anchorsattached to the substrate (1010). The static mass can be attached to theanchors by anchor suspension flexures. Method 1000 further includessuspending a dynamic mass of the micromachined gyroscope from the staticmass by one or more gyroscope suspension flexures (1020). The dynamicmass can surround the static mass.

In example implementations, in method 1000, suspending the static massin an x-y plane over the substrate 1010 includes suspending the staticmass over the substrate by a geometrically distributed arrangement ofthe plurality of anchors. The geometrically distributed arrangement ofthe anchors can average substrate deformation and average capacitivegaps between out-of-plane rate sense electrodes placed on the substrateand the dynamic mass.

In example implementations, in method 1000, suspending the static massin an x-y plane over the substrate includes suspending the static massover the substrate by a symmetrical arrangement of four anchors. Each ofthe four anchors can be attached to the substrate at about a same radialdistance from a center of the gyroscope.

Method 1000 may further include disposing one or more sense electrodeson the substrate. The one or more sense electrodes may be configured todetect x-axis and y-axis acceleration of the dynamic mass.

In example implementations, disposing one or more sense electrodesconfigured to detect x-axis and y-axis acceleration of dynamic mass onthe substrate can include disposing the one or more sense electrodes atabout a midway between a center of the gyroscope and an outer edge ofthe gyroscope, and disposing one or more in-plane drive electrodes andone or more sensing electrodes toward an outer edge of the gyroscope.

In example implementations, disposing one or more sense electrodesconfigured to detect x-axis and y-axis acceleration of dynamic mass onthe substrate can include disposing the one or more sense electrodesaway from the center of the gyroscope at about at about an edge of thegyroscope, and disposing one or more in-plane drive electrodes and oneor more sensing electrodes in a region of the gyroscope closer to thecenter of the gyroscope than the one or more sense electrodes configuredto detect x-axis and y-axis acceleration of dynamic mass.

It will also be understood that when an element, such as a transistor orresistor, or gyroscope component, is referred to as being on, connectedto, electrically connected to, coupled to, or electrically coupled toanother element, it may be directly on, connected or coupled to theother element, or one or more intervening elements may be present. Incontrast, when an element is referred to as being directly on, directlyconnected to or directly coupled to another element or layer, there areno intervening elements or layers present. Although the terms directlyon, directly connected to, or directly coupled to may not be usedthroughout the detailed description, elements that are shown as beingdirectly on, directly connected or directly coupled can be referred toas such. The claims of the application (if included) may be amended torecite exemplary relationships described in the specification or shownin the figures.

As used in this specification, a singular form may, unless definitelyindicating a particular case in terms of the context, include a pluralform. Spatially relative terms (e.g., over, above, upper, under,beneath, below, lower, and so forth) are intended to encompass differentorientations of the device in use or operation in addition to theorientation depicted in the figures. In some implementations, therelative terms above and below can, respectively, include verticallyabove and vertically below. In some implementations, the term adjacentcan include laterally adjacent to or horizontally adjacent to.

Implementations of the various techniques described herein may beimplemented in (e.g., included in) digital electronic circuitry, or incomputer hardware, firmware, software, or in combinations of them.Portions of methods also may be performed by, and an apparatus may beimplemented as, special purpose logic circuitry, e.g., an FPGA (fieldprogrammable gate array) or an ASIC (application-specific integratedcircuit).

Implementations may be implemented in a computing system that includesan industrial motor driver, a solar inverter, ballast, a general-purposehalf-bridge topology, an auxiliary and/or traction motor inverterdriver, a switching mode power supply, an on-board charger, anuninterruptible power supply (UPS), a back-end component, e.g., as adata server, or that includes a middleware component, e.g., anapplication server, or that includes a front-end component, e.g., aclient computer having a graphical user interface or a Web browserthrough which a user can interact with an implementation, or anycombination of such back-end, middleware, or front-end components.Components may be interconnected by any form or medium of digital datacommunication, e.g., a communication network. Examples of communicationnetworks include a local area network (LAN) and a wide area network(WAN), e.g., the Internet.

While certain features of the described implementations have beenillustrated as described herein, many modifications, substitutions,changes and equivalents will now occur to those skilled in the art. Itis, therefore, to be understood that claims, if appended, are intendedto cover all such modifications and changes as fall within the scope ofthe implementations. It should be understood that they have beenpresented by way of example only, not limitation, and various changes inform and details may be made. Any portion of the apparatus and/ormethods described herein may be combined in any combination, exceptmutually exclusive combinations. The implementations described hereincan include various combinations and/or sub-combinations of thefunctions, components and/or features of the different implementationsdescribed.

1. A micromachined gyroscope comprising: a substrate; a static masssuspended in an x-y plane over the substrate; a dynamic mass surroundingthe static mass and suspended from the static mass; at least oneout-of-plane rate sensing electrode disposed on the substrate at an edgeof the gyroscope; at least one in-plane drive electrode; and at leastone in-plane rate sensing electrode, the at least one in-plane driveelectrode and the at least one in-plane drive sensing electrode beingdisposed in a region of the gyroscope closer to a center of thegyroscope than the at least one out-of-plane rate sense electrode. 2.The micromachined gyroscope of claim 1, further comprising: a pluralityof anchors coupled with the substrate; and a plurality of anchorsuspension flexures coupling the static mass to the plurality ofanchors.
 3. The micromachined gyroscope of claim 2, wherein: the staticmass has an X-shape; and the plurality of anchors includes a symmetricalarrangement of four anchors, each anchor of the four anchors beingattached to the substrate at a same radial distance from a center of thegyroscope.
 4. The micromachined gyroscope of claim 3, wherein thedynamic mass is coupled with the static mass at bottoms of valleys ofthe X-shape by at least one gyroscope suspension flexure.
 5. Themicromachined gyroscope of claim 4, wherein the at least one gyroscopesuspension flexure including at least one C-beam flexure.
 6. Themicromachined gyroscope of claim 2, wherein the static mass is suspendedin the x-y plane over the substrate by a geometrically distributedarrangement of the plurality of anchors.
 7. The micromachined gyroscopeof claim 6, wherein the geometrically distributed arrangement of theplurality of anchors is configured to: track substrate deformation; andaverage capacitive gaps between the dynamic mass and out-of-plane ratesense electrodes disposed on the substrate.
 8. The micromachinedgyroscope of claim 1, further comprising at least one gyroscopesuspension flexure coupling the dynamic mass with the static mass. 9.The micromachined gyroscope of claim 1, wherein the at least oneout-of-plane sense electrode is configured to detect x-axis accelerationand y-axis acceleration of the dynamic mass.
 10. The micromachinedgyroscope of claim 1, wherein the at least one in-plane drive electrodeand the at least one in-plane drive sensing electrode are coupled withthe substrate by respective anchors.
 11. The micromachined gyroscope ofclaim 1, wherein: the at least one in-plane drive electrode includes apair of drive electrodes disposed on a first side of the static mass;and the at least one in-plane drive sensing electrode includes a pair ofdrive sensing electrodes disposed on a second side of the static mass,the second side being opposite the first side.
 12. The micromachinedgyroscope of claim 1, further comprising at least one in-plane ratesensing electrode.
 13. The micromachined gyroscope of claim 12, whereinthe at least one in-plane rate sensing electrode is configured to detectz-axis acceleration of the dynamic mass.
 14. The micromachined gyroscopeof claim 12, wherein the at least one in-plane rate sensing electrodeincludes: a first z-axis rate sensing electrode disposed on a first sideof the static mass; and a second z-axis rate sensing electrode disposedon a second side of the static mass, the second side being opposite thefirst side.
 15. A micromachined gyroscope comprising: a substrate; astatic mass suspended in an x-y plane over the substrate; a dynamic masssurrounding the static mass and suspended from the static mass; at leastone out-of-plane rate sensing electrode disposed on the substrate at anedge of the gyroscope; and at least one in-plane rate sensing electrode,the at least one in-plane rate sensing electrode being disposed in aregion of the gyroscope closer to a center of the gyroscope than the atleast one out-of-plane rate sensing electrode.
 16. The micromachinedgyroscope of claim 15, wherein the at least one in-plane rate sensingelectrode includes: a first z-axis rate sensing electrode disposed on afirst side of the static mass; and a second z-axis rate sensingelectrode disposed on a second side of the static mass, the second sidebeing opposite the first side.
 17. The micromachined gyroscope of claim15, further comprising: at least one in-plane drive electrode; and atleast one in-plane drive sensing electrode, the at least one in-planedrive electrode and the at least one in-plane drive sensing electrodebeing disposed in the region of the gyroscope closer to the center ofthe gyroscope than the at least one out-of-plane rate sensing electrode.18. The micromachined gyroscope of claim 17, wherein: the at least onein-plane drive electrode includes a pair of drive electrodes disposed ona first side of the static mass; and the at least one in-plane drivesensing electrode includes a pair of drive sensing electrodes disposedon a second side of the static mass, the second side being opposite thefirst side.
 19. The micromachined gyroscope of claim 15, wherein the atleast one in-plane rate sensing electrode is configured to detect z-axisacceleration of the dynamic mass.
 20. The micromachined gyroscope ofclaim 15, wherein the at least one out-of-plane rate sensing electrodeis configured to detect x-axis acceleration and y-axis acceleration ofthe dynamic mass.